WRITE THE GENERAL CHARACTERS OF THE CLASS MAMMALIA.
the general characterstics of class mammalia are :-
1. All the organisms of class mammalia have mammary glands.
2. They are warn blodded.
3. give birth to young ones instead of laying eggs.
4. presence of hair.
5. most organisms have specialised teeths.
6. heart is 4 chambered
Characteristics of Class Mammalia
1) Warm blooded.
2) Possess hair which is made of keratin. The evolution of mammalian keratin is believed to be independent of reptilian keratin. Hair provides insulation .
3) Endothermic. The majority of the heat energy is used to maintain their high body temperature.
4) Four chambered heart.
5) Mammary glands are used to produce milk to nourish their young. Female glands are the only functional glands.
6) Thediaphragm is a muscle that separates the thoracic cavity from the abdominal cavity.
7) Seven cervical vertebrae (neck bones) are present in most mammals.
8) Most are viviparous though some are oviparous. An extended gestation period uterine development is common in most placental mammals.
9) Teeth are imbedded in the jaw bone and come in a variety of forms.
10) Well developed brain.
11) Mammals developed from the therapsid ancestors during the Triassic period.
12) Mammals are heterodontic, meaning that their teeth are different shapes, except those with no teeth at all.
13) Reptiles and fish have teeth that are all basically the same, though they can vary in size throughout the mouth. See image above.
14) The Buccal Cavity (the mouth) has a false palate as a roof, meaning that the nostrils do not lead directly into his mouth.
15) The body is maintained at a constant temperature they generate heat within their bodies metabolically and also have special cooling mechanisms.
16) Highly developed neopallium.
17) Tectum reduced to corpora quadrigemina: functions mainly as a relay center for auditory information and to control visual reflexes.
18) Corpus callosum in eutherians provides additional communication
19) Smell acute except whales and higher apes.
20) Eye typical of amniotes.
21) Tapetum lucidum well developed in nocturnal mammals.
22) Touch- most have vibrissae that are controlled by facial muscles.
23) Lateral movement of jaw during mastication.
24) Viviparous except monotremes which are egg lying.
25) Parental care well developed.
Difference between mammals and aves
1. Mammals give birth to their young whereas birds lay eggs.
2. Birds have feathers whereas mammals have only fur or hair.
3. Birds have porous or hollow bones. In contrast, mammals have denser bones.
4. Birds have wings while mammals have paws, hands, and hooves.
5. Mammals produce sound using a larynx, but in birds this organ does not produce sounds. Instead, birds have a syrinx which serves as voice box.
6. Mammals feed their young milk produced by the mammary glands. On the other hand, the young birds are fed by the parents regurgitating partially digested food.
7. The lungs of birds do not expand or contract as that of the lungs of mammals. In mammals, the oxygen and carbon dioxide is exchanged in the alveoli which are microscopic sacs in the lungs. In birds, the exchange happens in air capillaries which are walls of microscopic tubules. While there is only a single respiratory cycle in mammals, there are two cycles in birds.
8. Birds have a nucleus in the RBS whereas it is not generally seen in mammals. If there is a nucleus in the RBS in mammals, then it is a sign of sickness. The RBS of birds are oval in shape whereas most of the mammals’ RBSs have a round shape.
•They are multicellular.
•Notochord is present
•Give birth to young ones.(except platypus and echidna)
•Respiration takes place trough lungs.
•Females have mammary glands present.
•They are warm blooded.
•External ears are present.
•Skin is provided with hairs, sweat glands and sebaceous glands.
•Have bone marrow.
•Wings are absent(except in bats)
•Have four chambered heart.
•Muscular diaphragm is present.
•Body is divisible into head, neck, trunk, and tail.
•Live in all kinds of habitats.
•Have high metabolism.
•Heart rates depends on the size of the animal(smaller=faster)
•Majority of mammals have 7 cervical vertebrae. The exceptions are the manatee and the two-toed sloth which have only 6 cervical vertebraes, and the three-toed sloth with 9cervical vertebraes.
•Are heterodontic, meaning their teeth are in different shapes.